Fermi lat observation of diffuse gamma rays produced through interactions between local interstellar matter and high-energy cosmic rays

Abdo, A. A.; Ackermann, M.; Ajello, M.; Atwood, W. B.; Axelsson, M.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Baughman, B. M.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bregeon, J.; Brez, A.; Brigida, M.; Bruel, P.; Burnett, T. H.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Carlson, P.; Casandjian, J. M.; Cecchi, C.; Celik, O. E.; Chekhtman, A.; Cheung, C. C.; Ciprini, S.; Claus, R.; Cohen Tanugi, J.; Conrad, J.; Cutini, S.; Dermer, C. D.; De Angelis, A.; De Palma, F.; Digel, S. W.; Do Couto, E. Silva E.; Drell, P. S.; Dubois, R.; Dumora, D.; Farnier, C.; Favuzzi, Cecilia; Fegan, S. J.; Focke, W. B.; Frailis, M.; Fukazawa, Y.; Funk, S.; Fusco, P.; Gargano, F.; Gasparrini, D.; Gehrels, N.; Germani, S.; Giebels, B.; Giglietto, Nicola; Giordano, F.; Glanzman, T.; Godfrey, G.; Grenier, I. A.; Grondin, M. H.; Grove, J. E.; Guillemot, L.; Guiriec, S.; Hanabata, Y.; Harding, A. K.; Hayashida, M.; Hays, E.; Hughes, R. E.; Johannesson, G.; Johnson, A. S.; Johnson, R. P.; Johnson, W. N.; Kamae, T.; Katagiri, H.; Kawai, N.; Kerr, M.; Knoedlseder, J.; Kocian, M. L.; Kuehn, F.; Kuss, M.; Lande, J.; Latronico, L.; Lemoine Goumard, M.; Longo, F.; Loparco, F.; Lott, B.; Lovellette, M. N.; Lubrano, P.; Makeev, A.; Mazziotta, M. N.; Mcenery, J. E.; Meurer, C.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Moiseev, A. A.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nolan, P. L.; Norris, J. P.; Nuss, E.; Ohsugi, T.; Okumura, A.; Omodei, N.; Orlando, E.; Ormes, J. F.; Ozaki, M.; Paneque, D.; Panetta, J. H.; Parent, D.; Pepe, M.; Pesce Rollins, M.; Piron, F.; Pohl, M.; Porter, T. A.; Raino, S.; Rando, R.; Razzano, M.; Reimer, A.; Reimer, O.; Reposeur, T.; Ritz, S.; Rochester, L. S.; Rodriguez, A. Y.; Ryde, F.; Sadrozinski, H. F. W.; Sanchez, D.; Sander, A.; Saz, Parkinson P. M.; Schalk, T. L.; Sellerholm, A.; Sgro, C.; Smith, D. A.; Smith, P. D.; Spandre, G.; Spinelli, P.; Starck, J. L.; Stecker, F. W.; Strickman, M. S.; Strong, A. W.; Suson, D. J.; Tajima, H.; Takahashi, H.; Takahashi, T.; Tanaka, T.; Thayer, J. B.; Thayer, J. G.; Thompson, D. J.; Tibaldo, L.; Torres, D. F.; Tosti, G.; Tramacere, A.; Uchiyama, Y.; Usher, T. L.; Vasileiou, V.; Vilchez, N.; Vitale, V.; Waite, A. P.; Wang, P.; Winer, B. L.; Wood, K. S.; Ylinen, T.; Ziegler, M.

doi:10.1088/0004-637X/703/2/1249

Observations by the Large Area Telescope (LAT) on the Fermi mission of diffuse gamma-rays in a mid-latitude region in the third quadrant (Galactic longitude l from 200 degrees to 260 degrees and latitude vertical bar b vertical bar from 22 degrees to 60 degrees) are reported. The region contains no known large molecular cloud and most of the atomic hydrogen is within 1 kpc of the solar system. The contributions of gamma-ray point sources and inverse Compton scattering are estimated and subtracted. The residual gamma-ray intensity exhibits a linear correlation with the atomic gas column density in energy from 100 MeV to 10 GeV. The measured integrated gamma-ray emissivity is (1.63 +/- 0.05) x 10(-26) photons s(-1)sr(-1) H-atom(-1) and (0.66 +/- 0.02) x 10(-26) photons s(-1)sr(-1) H-atom(-1) above 100 MeV and above 300 MeV, respectively, with an additional systematic error of similar to 10%. The differential emissivity from 100 MeV to 10 GeV agrees with calculations based on cosmic ray spectra consistent with those directly measured, at the 10% level. The results obtained indicate that cosmic ray nuclei spectra within 1 kpc from the solar system in regions studied are close to the local interstellar spectra inferred from direct measurements at the Earth within similar to 10%.

Fermi lat observation of diffuse gamma rays produced through interactions between local interstellar matter and high-energy cosmic rays / Abdo, A.A., Ackermann, M., Ajello, M., Atwood, W.B., Axelsson, M., Baldini, L., Ballet, J., Barbiellini, G., Bastieri, D., Baughman, B.M., Bechtol, K., Bellazzini, R., Berenji, B., Bloom, E.D., Bonamente, E., Borgland, A.W., Bregeon, J., Brez, A., Brigida, M., Bruel, P., et al.. - In: THE ASTROPHYSICAL JOURNAL. - ISSN 0004-637X. - 703:2(2009), pp. 1249-1256. [10.1088/0004-637X/703/2/1249]